Container scale

ABSTRACT

The present invention concerns a process and a device for carrying out the process for weight determination of the contents of containers (5), for example for garbage. Two swivel arms (2) that are lifted by hydraulic devices (3) are mounted on a garbage collecting vehicle (1). The container (5) is carried by a fork (4). Integrated into the swivel arm (2) is a force measuring apparatus that comprises two flexural members (7) supporting the main load, two spring tongues (8), and a force transducer (11) that is installed between two stilts (12) between the spring tongues (8). The flexural members (7) and the spring tongues together form an elastic stepdown; the force transducer (11) thus only measures that part of the total load flowing through it as given by the stepdown. Further, a gradient meter (16) is mounted on the swivel arm (2), that has the same action line W as the force measurement device integrated in the swivel arm (2). In this manner, the measurement of the weight of the container (5) is very extensively independent of the gradient. The weight of container (5) is calculated in known manner by two &#34;total weight-tare=net&#34; weighings. In order to exclude the influences of elastic prestresses, the angle range over which it is measured is limited to a preset degree. The container (5) is inserted in the fork (4) in the position L, position M is the measuring position, and the container (5) is emptied in position E (FIG. 1).

The present invention concerns a weighing device that swivels around anapproximately horizontal axis for use on hoisting equipment, such asmetering equipment, foundry ladles, and hoisting or emptying equipmentfor containers.

Several apparatuses of the listed type are known. Numerous patents havebeen granted for weighing devices, such as, e.g., stacker trucks inwhich only the loads being transported and simultaneously weighed needto be hoisted; apparatuses are further known in which the whole vehicleincluding hoisting device is weighed. Garbage container scales, whichare connected to a tilting device, are known from U.S. Pat. No.4,854,406 and German Patent 3,819,169 Al. While the apparatus disclosedin the German patent 3,819,169 Al belongs to the class of stacker truckweighing apparatuses, the U.S. Pat. No. 4,854,406, combined with a"total weight-tare=net weight" weight determination, teaches the use ofa large number of apparatuses for the weight determination of a varietyof garbage containers in which basically--as is shown from the data--a"total weight tare" weighing is performed. Two of the apparatusesdepicted in this U.S. patent in principle measure a torsional moment;the measurement result therefore is dependent on the position of thecenter of gravity of the garbage container. One of the describedapparatuses belongs in the class of stacker truck scales and in theweighing of tons of transportable garbage each apparatus is afflicted byundefinable frictional forces that are not measured simultaneously. Anexpensive operating concept with selected measuring positions defined bycam-actuated switches are common to all types. In rough operation, whichpredominates during the collection of garbage, malfunctions of thedescribed apparatuses are obvious.

The object which must be achieved by the present invention comprises thecreation of a weighing device with at least one swivel arm that willdetermine the weight of the container in normal operation of the unit ina suitable range independent of the position and movement.

The inventive concept, depending on several practical examples, will beexplained in more detail with use of the attached drawing.

There are shown:

FIG. 1 two practical examples as container scales,

FIG. 2 a detail of the second practical example,

FIGS. 3a, 3b a third practical example as foundry ladle scale.

A loading, tilting, and emptying mechanism comprising a swivel arm 2 anda hydraulic cylinder 3 is mounted on a garbage collecting vehicle 1.Both the swivel arm and hydraulic cylinder are constructed in duplicateand are connected to both sides of the garbage collecting vehicle 1. Agrab fork 4 is mounted on each swivel arm 2--as a rule rigidly. The grabfork for receipt of a portable container 5 is brought into anapproximately horizontal position and the container 5 is introduced intothe grab fork 4. Subsequently, the swivel arm 2 is swiveled on an axle 6located on the garbage collecting vehicle 1 by increase of the operatingpressure of the hydraulic cylinder 3 until the garbage falls out fromthe container 5. The specific designs of the garbage collecting vehicle1 with regard to the sliding cover and the container 5 will not bedescribed here since such designs do not involve the invention. Thisalso applies in corresponding manner for the following practicalexamples.

A part 6 designed as a parallelogram is found on swivel arm 2 and isintegrated into this. Two essentially parallel flexural members 7 formthe primary springs for an elastic stepdown. The part of the swivel arm2 lying between axle 6 and the flexural members 7 is designated asinternal section 9 and the part lying between the flexible springs 7 andthe grab fork 4 is designated as external section 10. The flexuralmembers 7 support the main portion of the weight force engaging theforward end of the one grab arm (therefore, the weight of the container5, the grab forks 4, and the external section 10). These load portionsare designated hereafter by "load". Two spring tongues 8 forming thesecondary springs of the cited elastic stepdown run essentially parallelto the flexural members 7; the upper spring tongue 8 in this practicalexample proceeds from the internal section 9 and the lower tongueproceeds from the external section 10. A force transducer 11 isinstalled between the spring tongues 8 by means of two stilts 12.Without limitation, the force transducer 11, for example, comprises atype with at least one laterally oscillating wire. As a result of themethod of construction of the load measuring apparatus comprising theflexural members 7, the spring tongues 8, and the force transducer 11,only forces or force portions are measured that proceed in an actionline designated by W. Also, the two stilts 12 lie in this action line W;the flexural members 7 and the spring tongues 8 proceed essentiallyperpendicular to the action line W. If the external section 10 isstressed, the flexural members 7 bend downward. In this manner, atensile force now acts between the spring tongues 8, or, in case ofprestressing by compression, this prestressing force now is reduced. Thelow intrinsic elasticity of the force transducer 11 is a component ofthe resilience of the spring tongues 8.

One variant of the drawn arrangement comprises the attachment of theupper spring tongue 8 to the external section 10 and the lower springtongue 8 to the internal section 9. Then, a compressive force betweenthe spring tongues 8 can cause a load on the external section 10.

In the emptying process, essentially three positions are differentiated.In the first position designated by L the container 5 is inserted intothe grab fork 4. When it is subsequently lifted to such a height that itno longer contacts the ground, a force considerably lower than the loadacts on the described load measuring device in the direction of theaction line W. The measured force rises during the lifting process untilit reaches its maximum at the position of swivel arm 2 designated by M;then, i.e., when the action line W coincides with the direction of theacceleration of gravity. Upon further lifting of the swivel arm 2, themeasured force decreases.

The measuring process linked with the described practical examplecomprises a continuous determination of the force acting in thedirection of the action line W during the swiveling process and acomparison of each measuring result to the foregoing result. The maximumresult corresponds to the load. The same pattern is followed duringlowering of swivel arm 2--after emptying of the container 5. Thedifference of the two maximum values corresponds to the net load, inother words, the weight of the emptied garbage. The electronic computerequipment necessary for the weight determination and sequence control isknown per se and are not depicted here.

Obviously, the inventive concept includes the lifting of an initiallyempty container 5, charging it in the lifted position, for example, witha metering device, and subsequently lowering it again when full. Thetare weighing then is accomplished initially and the total weighingsubsequently.

Also, the inventive concept contains the summation of the measuringresults from the two load measuring devices that are provided in aweighing device according to the invention with two swivel arms 2.

A second practical example of the inventive concept will be described byuse of a part of FIG. 1 not mentioned previously, and in more detail byuse of FIG. 2. A panel 14 that bears a schematically depicted case 15 isattached on the internal section 9 of the swivel arm 2, for example bymeans of screws 13. This case--as depicted in FIG. 2--contains anacceleration meter 16 having a frame 24 that, for example, is screwedonto the panel. The acceleration meter 16 comprises a standard weight 19that is directed to the frame 24 by means of two essentially parallelguide bars 20. The component of the weight force of the standard weight19 acting in the direction of the action line W presses on a forcetransducer 21 through a first stilt 22 that is supported on the frame 24through an additional stilt 23. The two stilts 22, 23 located one underthe other proceed along the same axis that also agrees with thedirection of the action line W and the direction of the virtual movementof the standard weight 19. The force transducer 21 is preferably of thesame type as the force transducer 11, therefore, however withoutlimitation, of a type with at least one laterally oscillating wire. Thedimensions of the panel 14 are such that the action lines W of the twoforce transducers 11, 21 coincide or at least are parallel. In thismanner, as a result of the obligatory, identical inclination angle, thesame fractions of the weight forces acting on them will be measured bythe two force meters--therefore the acceleration meter 16 and the meterthat is integrated in the swivel arm 2. The weight force of the standardweight 19 is normalized mathematically to the value "1" that correspondsto the vertical position of the action line W. Now, if the swivel arm 2is rotated, or the garbage collecting vehicle 1 stands at an angle--inone or both axes--the ratio of the measured forces remains constant.Therefore, in this case it represents a true weighing in the sense of aweight comparison.

Since elastic prestressing forces can be accompanied by small deviationsof the constancy of the weight ratios, it is suitable to limit themeasuring range, for example, to an angle of ±20° with reference to thevertical direction of the action line W. This is achieved by settinglimits for the measuring results of the acceleration meter 16. A limitof 0.940 with a normalization to 1.000 corresponds to a limitation ofthe measuring range of approximately ±20°.

The arrangement according to FIGS. 1 and 2 also has an advantage in thatthe acceleration states during tilting do not have to be considered.Further, it is mathematically possible by known means to extensivelyeliminate any effects of rockings that occur during operation.

The measuring process corresponding to the second practical exampleaccording to FIGS. 1 and 2 therefore depends on the formation of theratio of the results of the two force measuring devices with limitationto a suitable angle range for example of ±20 to the vertical directionof the action line W. The weight calculation for the garbage isaccomplished by a total weighing during lifting of the container 5 and atare weighing upon lowering after emptying.

Also, in this process, the inventive concept includes summation of themeasuring results of the two loading measuring devices that are providedwith a weighing device with two swivel arms 2 according to theinvention.

FIGS. 3a and 3b depict a third practical example. The swivel arm 2 withintegrated loading measuring apparatus and the acceleration meter 16 inthis case are a component of a lifting and tilting apparatus for foundryladles that are mounted on an appropriate, schematically representedtransport vehicle 27. The swivel arm 2 bears a fork 26 that receives afoundry ladle 25. The swivel arm 2 is tilted by hydraulic device 28 andthus the foundry ladle 25 is brought into operating position. In thesame manner as in the first practical example, the swivel arm 2,hydraulic device 28, and the force meter integrated into the swivel armare constructed in duplicate. Since the apparatus according to theinvention only measures the forces parallel to the action line,displacements of the center of gravity that occur during pouring falloutside of consideration. The same certainly also applies for the otherpractical examples.

Also, a metering container that can receive or deliver dischargeablematerials can be used in place of the foundry ladle 25.

A great advantage of the weighing apparatus according to the inventionlies in that the swivel arm 2 of the various lifting apparatuses can beequipped or retrofitted easily and troublefree into the structure andmechanics of the swivel arms as long as the design takes thispossibility into consideration from the outset.

Further, maintenance and replacement operations on the force meters arefacilitated to a high degree in all cases since the swivel arms need notinfluence the design.

I claim:
 1. Weighing device for a lifting apparatus for containers (5),which swivel on an approximately horizontal axis (6), with at least oneswivel arm (2) and electronic devices for calculation and storage of theweighing results, characterized by the fact thatthe swivel arm (2) isintegrated with a force measuring apparatus, through which the entireforce flow of the swivel arm passes; this apparatus comprisesessentially two parallel flexural members (7), which together form theprimary spring of an elastic stepdown, and two spring tongues (8) lyingone below the other parallel to the flexural members (7), which togetherform the secondary spring of the elastic stepdown; a force transducer(11) is installed between these spring tongues (8), whose forcemeasuring direction defines an action line W, in which one spring tongue(8) is mounted on the swivel arm (2) on the axle part and the otherspring tongue is mounted on the load-bearing part, the two flexuralmembers (7) are components of the swivel arm (2) and thus are integratedtherein so that they lie horizontally during a central operatingposition of the swivel arm (2), the force transducer (11) is installedbetween the spring tongues (8) in such manner that the force acting onit (therefore also the action line W), is perpendicular to the directionof the flexural members (7), to measure a vertically proceeding force inthe central operating position of the swivel arm (2).
 2. Weighing deviceaccording to Patent claim 1, characterized by the fact that the upperspring tongue (8) in the central operating position of the swivel arm(2), is mounted on the axle side of the swivel arm (2) and the lowerspring tongue (8) is mounted on the load side.
 3. Weighing deviceaccording to patent claim 1, characterized by the fact that the lowerspring tongue (8) in the central operating position of the swivel arm(2) is mounted on the swivel arm (2) on the axle side and the upperspring tongue (8) is mounted on the load side.
 4. Weighing deviceaccording to patent claim 1, characterized by the fact that the forcetransducer (11) is a force transducer with at least one laterallyoscillating wire.
 5. Weighing device according to one of the patentclaims 1 through 4, characterized by the fact that the weighing deviceexhibits two parallel-operating swivel arms rotatable around the sameaxis (6).
 6. Weighing device according to patent claim 5, characterizedby the fact that the measuring results of the two force transducers (11)are added for calculation of the total weight.
 7. Weighing deviceaccording to patent claim 1, characterized by the fact thatanacceleration meter (16) is present and is attached to swivel arm (2),this acceleration meter (16) comprising a frame (21) on which a standardweight (19) is introduced in controlled path by means of two essentiallyparallel guide bars (20); the weight presses through a first stilt (22)onto a force transducer (21) that is supported on the frame (24) by asecond stilt (23), the two stilts (22, 23) located one below the otherlie in the same axis that also is the direction both of the virtualmovement of the standard weight (19) and that of the action line W. 8.Weighing device according to patent claim 7, characterized by the factthat the force transducer (21) is a force transducer with at least onelaterally oscillating wire.
 9. Process for calculation of the weight ofthe contents of a container (5) lifted by a weighing device according topatent claim 1 and having at least one swivel arm (2), characterized bythe fact thatduring the lifting process of the full container (5), theforce acting on the force transducer (11) is measured continuously andis calculated and stored by the electronic computer, each measuringresult is compared to the prior and successive results, the highestmeasured result is designated as the weight of the full container (5),after emptying of the container (5), the force acting on the forcetransducer (11) again is measured continuously and is calculated andstored by the electronic computer, each measuring result is compared tothe prior and successive results, the highest measured result isdesignated as the weight of the empty container (5), the difference ofthe two highest results calculated in this manner is designated as theweight of the contents of the container (5) and is stored.
 10. Processfor calculation of the weight of the contents of a container (5) liftedby a weighing device according to patent claim 1 having at least oneswivel arm (2), characterized by the fact thatduring the lifting processof the empty container (5), the force acting on the force transducer(11) is measured continuously and is calculated and stored by theelectronic computer, each measuring result is compared to the prior andsuccessive results, the highest measured result is designated as theweight of the empty container (5), after filling of the container (5)again the force acting on the force transducer (11) is measuredcontinuously and is calculated and stored by the electronic computer,each measuring result is compared to the previous and the successiveresults, the highest measured result is designated as the weight of thefull container (5), the difference of the two highest results calculatedin this manner is designated as the weight of the contents of thecontainer (5) and is stored.
 11. Process for calculation of the weightof the contents of a container (5) lifted by a weighing device with atleast one swivel arm (2) according to Patent claim 7, characterized bythe fact thatthe weight of the standard weight (19) with flexuralmembers (17) standing horizontally is normalized mathematically to1.000, during the lifting process the ratio of the forces measured bythe force transducer (11) of the load measuring apparatus and the forcetransducer (21) of the acceleration meter (16) is generatedmathematically and the lifted load is calculated from this, afterfalling below a preset deviation from the value 1.000 for the measuringresult of the acceleration meter (16), the mean is formed from a presetnumber of weighing results and the mean is stored as valid weightresult, the difference of the valid weight results that are calculatedand stored during lifting and lowering of the swivel arm (2), isgenerated; this corresponds to the weight of the contents of thecontainer (5).
 12. Process according to patent claim 11, characterizedby the fact that, with the presence of two swivel arms (2), the sum ofthe results is generated.
 13. Process according to patent claim 11,characterized by the fact that the preset deviation amounts to 0.040.14. Process according to patent claim 11, characterized by the fact thatthe preset deviation amounts to 0.13.
 15. Process according to patentclaim 11, characterized by the fact that the preset deviation liesbetween 0.02 and 0.13.